Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/359—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using near infrared light
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/3563—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing solids; Preparation of samples therefor
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/85—Investigating moving fluids or granular solids
  • G01N21/8507—Probe photometers, i.e. with optical measuring part dipped into fluid sample

Definitions

• This invention relates to a NIR spectroscopy method for analysis of chemical process components, e.g. for analysis of bitumen and solvent-diluted bitumen from froth treatment during oil sands processing.
• bitumen froth treatment is an essential step for removing water and solids from bitumen froth to produce bitumen meeting product specifications.
• the bitumen froth usually contains about 60 wt% bitumen, 30 wt% water, and 10 wt% solids.
• Current commercial froth treatment employs naphtha dilution followed by multistage centrifugation, which gives a diluted bitumen product typically containing about 0.3 to 1.0 wt% solids and about 1 to 5 wt% water.
• An alternative froth treatment process uses aliphatic solvent as froth diluent.
• a diluted bitumen product that contains less than 0.1 wt% water and solids and controlled levels of asphaltenes can be produced. It has previously been shown that, the performance of the froth treatment process using aliphatic solvent depends greatly on controlling process parameters; among the most important of these are the solvent-to-bitumen ratio (S/B, by wt), asphaltenes rejection level, and density of the solvent-diluted bitumen oil phase.
• Successful control of these process parameters ensures the desired level of asphaltenes in product, sufficient settling flux of water and solids, and on-spec product (e.g., containing less than 0.1 wt% water plus solids).
• the S/B of solvent-diluted bitumen is determined by vacuum rotary evaporation (Rotavapor), the asphaltenes content of bitumen is analyzed using the standard ASTM or IP methods that are based on precipitation of asphaltenes by light aliphatic solvent and followed filtration, and the density of solvent-diluted bitumen is measured using a laboratory density meter.
• Rotavapor vacuum rotary evaporation
• ASTM or IP methods that are based on precipitation of asphaltenes by light aliphatic solvent and followed filtration
• the density of solvent-diluted bitumen is measured using a laboratory density meter.
• NIR Near-infrared spectroscopy
• PCA Principal component analysis
• PLS partial least squares in latent variables
• U.S. Patent 5,742,064, issued April 21, 1998 describes a system for detecting water and dirt in petroleum flowing through a pipeline. Light is projected into the petroleum and light which is not absorbed by impurities contained in the petroleum is transmitted to a photomultiplier or spectrometer. Three different optical waveguides are used and the light source is a tunable laser.
• Heint et al. U.S. Patent 6,300,633, issued October 9, 2001, describes an inline spectrometric method for determining the residue content of an isocyanate. It uses a probe capable of directing light at wavelengths of from 1050 to 2150 nm into a process stream. A near-infrared spectrum is generated and the residue content is determined using a chemometric model. It is an object of the present invention to provide a method for using NIR spectroscopy for analysis of bitumen and solvent-diluted bitumen samples from the bitumen froth treatment process, that can be used for fast routine and on-line analysis.
• This invention relates to the use of NIR spectroscopy for the analysis of chemical compositions, and particularly for the near real time analysis of chemical process components during continuous processing.
• NIR spectra are correlated to the reference analytical data using chemometric techniques, e.g. methods based on eigenvalue decomposition of a data matrix.
• Techniques that may be used include principal component analysis (PCA) and partial least squares in latent variables (PLS).
• an NIR system comprising a double-pass transflectance probe coupled via fiber- optic cables to a stable white light source and a spectrograph. It is also advantageous to use a spectrograph with no moving parts and a probe with a long light path to minimize some secondary temperature effects.
• the probe is inserted into a material to be analyzed and a beam of stable white light is directed into the probe.
• the spectra obtained are recorded in the spectrograph and correlated to stored analytical data to provide a direct measurement of the feature of the material being analyzed. In this manner, the amounts of particular components in the material being analyzed may be determined, as well as other characteristics of the material, such as density, etc.
• NIR spectroscopy according to this invention is used in process control and optimization of bitumen froth treatment during oil sands processing.
• the NIR spectroscopy according to this invention provides the necessary rapid analysis of the asphaltenes content in the bitumen product, as well as the solvent-to-bitumen ratio, and the density of the solvent-diluted product.
• a froth is formed and the froth is treated to remove water and solids to produce a clean bitumen.
• the treatment of the froth includes a first dilution stage in which the froth is diluted with an aliphatic solvent before conducting steps to remove water and solids and thus obtain a clean bitumen product.
• An NIR spectroscopic system comprising a double-pass transflectance probe coupled via fiber-optic cables to a stable white light source and a spectrograph. The probe is inserted in a bitumen or solvent-diluted bitumen sample generated from the bitumen froth treatment and a beam of stable white light is directed into the probe.
• the spectra obtained are recorded in the spectrograph. These spectra are compared with stored reference data for one or more of (a) asphaltenes content in the bitumen product, (b) solvent-to- bitumen ratio of a solvent-diluted bitumen and (c) density of a solvent-diluted bitumen, to provide direct values of each.
• the white light preferably has a wavelength in the range 900 to 1700 nm and a light pass length in the range of 0.1 to 20 mm, preferably 1 to 10 mm, is used.
• Fig. 1 is a schematic illustration of an NIR spectroscopy arrangement according to the invention
• Fig. 2 shows NIR spectra of bitumen, maltenes and asphaltenes
• Fig. 3 is a graph showing relative standard deviation of asphaltene absorptivity in various asphaltene-toluene concentrations
• Fig. 4 shows forty toluene spectra recorded over a period of two weeks
• Fig. 5 is a graph showing standard deviation of absorbance for the forty spectra of Fig. 4
• Fig. 6 is a graph comparing predicted asphaltene content with actual analytical results for 0 to 20 wt% asphaltenes content
• Fig. 7 is a graph comparing predicted asphaltene content with actual analytical results for 20 to 100 wt% asphaltene content
• Fig. 8 is a graph showing the predicted density of solvent-diluted bitumen solution vs the value determined using a density meter
• Fig. 9 is a graph showing the predicted S/B of solvent-diluted bitumen solution vs the reference S/B;
• Fig. 10 is a typical NIR spectrum of a solvent-diluted bitumen sample and the PLS calibration coefficient for S/B;
• Fig. 11 is a three dimensional representation of the first three PCA spectral scores of diluted bitumen spectra.
• Fig. 12 is a two dimensional map showing the first two PCA spectral scores.
• FIG. 1 A schematic illustration of the NIR spectroscopy system for carrying out the invention is shown in Fig. 1.
• the material to be analyzed is carried in plant line 10 and a double-pass transflectance probe 11 extends through an opening into line 10.
• the probe 11 is coupled with a stable light source 14 an array detector 15 and a spectrograph 13 with no moving parts byway of fiber-optic cables 12.
• the computer 16 holds stored reference data and the recorded spectra are compared to the stored reference data to simply compute a direct value for the particular analysis being carried out.
• the froth treatment process using aliphatic solvent produces a clean solvent- diluted bitumen product and a sediment phase containing mainly water, solids, and precipitated asphaltenes.
• Solvent-diluted bitumen samples from both batch and continuous pilot tests were used in a test program. The batch test procedure was described in Long Y, Dabros T, Hamza H, "Stability and settling characteristics of solvent-diluted bitumen emulsions", Fuel, 2002;81(15): 1945-52.
• the pilot operation was performed in a froth treatment pilot plant, at CANMET Energy Technology Centre - Devon, Alberta. A mixture of pentane and hexane was used as solvent for all tests.
• Bitumen from the solvent-diluted bitumen product was recovered by removing solvent using a Rotavapor (vacuum rotary evaporator). This bitumen contained 0 to 20 wt% asphaltenes. Bitumen from the froth treatment sediment phase was also recovered by extraction with toluene following rotary • evaporation of the toluene-diluted bitumen solution. The bitumen from the sediment phase contained 20 to 100 wt% asphaltenes.
• Tests were conducted using the NIR spectrograph arrangement shown in Fig. 1. It comprised a spectrograph that had no moving parts, a linear array detector, a stable light source, and a double-pass transflectance probe with fiber-optic cable coupling the light source and the spectrograph.
• the wavelength range was 900 to 1700 nm.
• Sample spectra were recorded by directly dipping the transflectance probe into sample solutions.
• the solvent-diluted bitumen samples were measured directly with a 2-mm light path length probe without further dilution.
• the bitumen, asphaltenes, and maltenes samples were diluted with solvent (toluene or CS 2 ) and the measurement was done with a 10-mm light pass length probe.
• Sample classification was examined using PCA scores.
• the singular value decomposition (SND) algorithm was used.
• the optimal rank was determined by evaluating the reduced eigenvalues of the eigenvectors.
• the calibration models were validated either by using the "leave-one-out cross validation” method or by using an independent validation data set.
• the standard error of calibration (SEC) was calculated when the leave-one-out cross validation method was used and the standard error of validation (SEN) was calculated when an independent validation data set was used:
• n is the number of data points
• yp is the predicted result according to the model
• y R is the reference analytical result.
• the absorption bands of organic compounds in ⁇ IR region are the molecular vibrational transition (mainly due to the C-H, ⁇ -H, and O-H bonds) overtones and combinations.
• Table 1 lists the C-H absorptions and relative absorption intensities. In general, the higher the overtone order, the lower the absorption intensity. Therefore, the higher-order overtone bands should be used if a longer light path length for recording spectra is preferred for easier sample preparation and higher signal reproducibility. In this work, the second-order overtone and combination bands (1000 to 1600 nm) were used.
• Figure 2 shows the representative ⁇ IR spectra for oil sands bitumen (3 wt% solution in CS ), asphaltenes (0.2 wt% solution in CS ), and maltenes (20 wt% solution in CS ) from 1000 to 1600 nm.
• the maltenes spectrum clearly shows the second-order C-H overtone features at around 1200 nm and the combination band at around 1400 nm.
• the asphaltenes spectrum shows only a broad band across the whole spectral range without significant C-H overtone peaks. The light absorption of the asphaltenes was much stronger than that of the maltenes.
• the Athabasca oil sands bitumen contained 17.5 wt% asphaltenes and the rest was maltenes.
• the bitumen spectrum feature was dominated by asphaltenes absorption characteristics and the bitumen and asphaltenes spectra were very similar.
• Asphaltenes are the heaviest bitumen fraction with condensed aromatic-ring structures. It is believed that they stay in solution as a colloidal dispersion. Therefore, the apparent NIR absorption of asphaltenes can arise from both electronic transition of the condensed-aromatic structure and light scattering by the colloidal asphaltenes particles. It is of interest in this work to know which mechanism dominates, as light absorbance due to electronic transition usually has a good linear relationship with concentration; on the other hand, the light scattering intensity of asphaltenes is expected to depend on many conditions such as solvent type and solvent dilution ratio.
• Asphaltenes-toluene solutions were prepared with various asphaltenes concentrations (0.08, 0.13, 0.22, 0.44, and 0.87 g/100 mL). NIR spectra of these samples and pure toluene were recorded using a 10-mm light path length transflectance probe. The contribution of toluene to the absorbance was subtracted by calculating the difference of the sample solution spectra and the pure toluene spectrum (considering the dilution factor). Absorptivities of asphaltenes were calculated as:
• Figure 7 shows the prediction results for 20 to 100 wt% asphaltenes content.
• the model used two PLS components and exhibited an SEC of 1.1 wt%.
• EXAMPLE 5 This is a study on determining the density of solvent-diluted bitumen.
• This example is a study on deterrnining the solvent-to-bitumen ratio (S/B) of solvent-diluted bitumen.
• S/B is one of the most important operating parameters to be monitored and controlled in commercial froth treatment. It affects product quality (water content, solids content, asphaltenes rejection level), bitumen recovery, and the settling rates of water and solids.
• Figure 9 shows the results of S/B predictions using ⁇ IR. The wavelength range from 1040 to 1600 nm was used and three PLS components were sufficient to generate a reliable calibration model. An SEC of 0.1 was obtained.
• Figure 10 shows a typical ⁇ IR spectrum of a solvent-diluted bitumen sample and the PLS calibration coefficient for S/B. The 1040 to 1150 nm wavelength range was taken as negatively correlated to S/B, as light absorption in this range was dominated by bitumen. The absorptions at around 1200 nm and 1400 nm were characteristic of hydrocarbon solvent, and were positively correlated to S/B.
• FIG. 11 shows the first three PCA spectral scores of the clean diluted bitumen samples (containing less than 0.1 wt% water plus solids). The data points were located along a U-shaped corridor.
• the left-hand side of the graph is the region of high S/B (starting from-4.0), low density, and high asphaltenes content; the right-hand side is the region of low S/B (starting from 1.5), high density, and high asphaltenes content.
• Figure 12 is a 2-D map showing the first two PCA spectral scores.
• Region one is the clean product region.
• the solvent-diluted bitumen products are clean (containing less than 0.1 wt% water and solids) as long as the data point remains confined to this region.
• the data point will jump from Region one to Region two if process upset occurs.
• the time that is needed for a data point to move from one region to the other is an indication of the system response time (or residence time).
• the method of this invention when used for the analysis of bitumen streams given exceptionally accurate results.
• it gives an absolute accuracy of 0.2 wt% or better for 0 to 20 wt% asphaltenes content streams, 1.1 wt% or better for higher than 20 wt% asphaltenes content streams, absolute error of 0.1 or better for measurement of solvent-to-bitumen ratio and absolute error 0,0017 g/ml or better for measurement of the density of solvent-diluted bitumen.

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• 2003
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